Drug dispensing wound dressing

ABSTRACT

The disclosed wound dressings have a drug dispersed throughout a polyurethane matrix that is the reaction product of: (A) An isocyante terminated prepolymer formed by reaction of isophorone diisocyanate and a marcoglycol and (B) a monomer containing hydroxyl and vinyl groups. The reaction product is a vinyl terminated polyurethane oligomer which is liquid at room temperature and which may be readily admixed with a pharmacoactive substance and a photosensitizer, formed into a film and cured by exposure to UV light without release of heat. 
     In the most preferred embodiments the foregoing oligomer is codissolved in an organic solvent with a polyurethane polymer which is the reaction product of: 
     dicyclohexyl methane diisocyanate; 
     a polytetramethylene ether polyol having a molecular weight in the range of 1000-3000 daltons; and 
     1,4-butane diol. 
     That solution is then admixed with the pharmacoactive agent, formed into a film and cured.

BACKGROUND OF THE INVENTION

There has long been a need for a wound dressing which is soft, pliableand elastic, yet high in tensile strength and abrasion resistance andwhich can release drugs at a controlled, sustained level.

Presently available bandages made of materials such as cotton areundesirable because they retain water, serve as growth mediums forbacteria, and soak up tissue pieces and blood which clots, causingadhesion to the wound and trauma during removal.

Other bandages are made with plastic coverings with an adhesion coatingto decrease the undesirable water absorption of cotton wound dressings.Unfortunately, new problems were created due to lack of oxygentransmission through the plastic coating. Indeed, holes had to bepunched through the plastic covering to allow the transmission of someoxygen to the skin below. Hard plastic or silicone coatings were alsoapplied to the side of the bandage adjacent to the wound to preventadhesion. These coatings did not significantly decrease the problem ofthe bandage sticking to the wound, and blocked oxygen and watertransmission.

In further attempts to overcome the adhesion and permeability problems,polyurethane and other plastic dressings were tried. For example, U.S.Pat. No. 3,975,567 to Lock discloses a pressure and heat-treatedpolyurethane foam which is lyophilic.

Other polyurethanes which polymerize upon exposure to ultraviolet lightwere also developed. The majority of these UV-curable polyurethanes weredesigned for use as orthopedic casts, e.g., U.S. Pat. No. 4,209,605.Other types of polymers have been used as matrices for incorporation ofbiologically active agents and, in the form of polymerized sheets orfilms, have been used as wound dressings, such as the compoundsdisclosed by U.S. Pat. Nos. 4,321,117 (acrylic polymers) and 4,156,067(polyurethane). None of these compositions managed to combine theproperties of softness, oxygen and water vapor permeability,flexibility, thixotropy and capability for incorporation of biologicallyactive agents, with a fast cure at room temperature to a tough,colorless film. The ability to cure at room temperature without releaseof heat is particularly important because many drugs are heat labile.

At present, the most commercially successful burn and superficial skinwound dressing is a polyether-based polyurethane, moisture-vaporpermeable membrane compounded with silica gel. The composition, known as"Op-Site"®, described in U.S. Pat. Nos. 4,340,043 and 4,460,369 assignedto Smith & Nephew Research Ltd., is in the form of a thin film having asurface coated with a polyvinylethylether adhesive. Althoughconsiderably more comfortable, permeable, and effective as protectionagainst bacterial contamination than the prior art wound dressings, thismaterial still suffers from the inability to incorporate biologicallyactive agents such as coagulants and antibiotics into the membrane,rather than into the adhesive, and from difficulty in formation andapplication as a bandage which conforms to the contour of the site ofapplication. In connection with this latter problem, two to three peopleare required for application.

It is therefore an object of the present invention to provide a wounddressing which physically incorporates drugs such as antibiotics,coagulants, and anti-inflammatories into the dressing structure havingappreciable tensile strength rather than into the adhesive or thincoating on the dressing so that the drugs are released in a controlled,sustained manner.

It is a further object of the present invention to provide a materialfor use as a wound dressing which is strong yet flexible, and which canbe made to conform to the shape of the site of the wound.

It is a still further object of the present invention to provide such amaterial for use as a wound dressing which is nontoxic,non-carcinogenic, and biocompatible.

It is a further object of the present invention to provide a materialwhich can be easily formed and applied to a wound by one person inadverse circumstances.

Yet a further object of the invention is to provide a polymeric materialwhich is a liquid at room temperature and which has a sufficiently lowviscosity at room temperature (prior to cure) to facilitate admixturewith a drug to form a homogeneous blend.

Still a further object is to provide such a polymeric material whichcures at room temperature without release of heat (non-exothermic).

The foregoing and other objects and features of the claimed inventionwill be understood by those skilled in the art from a reading of thedescription which follows.

SUMMARY OF THE INVENTION

A polyurethane has now been discovered which is compatible with a widerange of pharmacoactive agents and which, in the form of an oligomer(uncured) which is a liquid at room temperature, may be admixed inliquid state with one or more pharmacoactive agents. Because the cure isnot exothermic to any appreciable degree, curing may be conductedwithout cooling and with no increase in temperature. The curedpolyurethane elastomer is crystal clear, soft and elastomeric. Appliedto a wound in the form of a film, the polyurethane serves to release theincorporated drug at a controlled, sustained rate while protecting thatportion of the incorporated drug yet to be released. The polyurethaneproduct is hydrophilic in nature and solvent resistant.

More specifically, the wound dressings of the present invention have adrug dispersed throughout a polyurethane matrix that is the reactionproduct of:

A. an isocyanate terminated prepolymer formed by reaction of isophoronediisocyanate and a macroglycol; and

B. a monomer containing hydroxyl and vinyl groups. This reaction productis a vinyl terminated polyurethane oligomer which is liquid at roomtemperature. This liquid oligomer may be readily admixed with apharmacoactive substance and a photosensitizer, formed into a film andcurved by exposure to UV light without release of heat.

In the most preferred embodiments the foregoing oligomer is codissolvedin an organic solvent with a polyurethane polymer which is the reactionproduct of: dicyclohexyl methane diisocyanate; a polytetramethyleneether polyol having a molecular weight in the range of 1000-3000;Daltons and 1,4-butane diol. The pharmacoactive agent and photoinitiatorare then admixed into the solution and a film is formed and cured.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

At the outset, the invention is described in its broadest overallaspects with a more detailed description following.

The drug dispensing composition of the present invention is formed byreacting isophorone diisocyanate and a macroglycol together to form anisocyanate terminated prepolymer and then reacting the prepolymer with achain terminator to form a vinyl terminated polyurethane oligomer. Thedrug and, optionally, a photoinitiator may be admixed with the foregoingcompounds at any point prior to curing to form a homogeneous admixture.The homogeneous admixture is formed into a liquid film and cured to formthe wound dressing with one side of the cured film optionally providedwith a pressure sensitive adhesive.

The isophorone diisocyanate (IPDI) used in the present invention is analiphatic compound having the following formula: ##STR1## IPDI isutilized in the present invention because it is a liquid at roomtemperature, because it cures to a crystal clear product upon exposureto ultraviolet light, rather than yellowing as is the case with manyprior art diisocyanates, and because it cures without any temperaturerise.

The macroglycol preferred for use in the present invention is apolypropylene glycol (PPG), preferably having a molecular weight of500-5000 daltons and, more preferably 1000-3000 daltons. PPG ispreferred because it reacts with the IPDI at a fast rate at roomtemperature with no temperature rise. Other high molecular weightglycols such as polyethylene glycol (PEG) may be employed, but PEG is asolid at room temperature and a feasible rate of reaction would requireheating. As used herein, the term "macroglycol" has reference to anyglycol having a molecular weight in excess of 500 daltons.

The chain terminator used in formulating the products of the inventionshould have both hydroxyl and vinyl functional groups and is preferablyan acrylic compound such as hydroxyethyl acrylate or hydroxyethylmethacrylate. Hydroxyethyl methacrylate (HEMA) is most preferred for useas the chain terminator.

A large variety of drugs, including heat labile drugs, may beincorporated into the compositions of the present invention at any pointwithin the formulation/reaction sequence because the process of thepresent invention does not involve any exothermic reaction and,therefore, no cooling of any reaction mixture is required prior to theaddition of a drug having activity highly susceptible to degradation byheat. However, it is preferred that the drug be added to the uncuredliquid, vinyl-terminated oligomer as the last additive prior to curingand after aeration for removal of all entrained gases. It iscontemplated that any coagulant, antibiotic, antifungal agent, topicalanesthetic, anti-inflammatory agent or mixture thereof might beincorporated into any one of the liquid precursors of the cured product.In the examples which follow thrombin is mentioned as a coagulant andgentamycin sulfate is mentioned as a wide-spectrum antibiotic but thosespecifically mentioned drugs are merely exemplary of the wide range ofdrugs that would be useful here.

Photosensitizers useful herein include benzophenone, acteophenone,azobenzene, acenaphthenequinone, o-methoxy benzophenone,thioxanthen-9-one, xanthen-9-one, 7-H-Benz(de) anthracen-7-one,1-naphthaldehyde 4,4'-bis(dimethylamino)benzophenone, fluorene-9-one,1'-acetonaphthone, 2'-acetonaphthone, anthraquinone, 2-tert.-butylanthraquinone, 4-morpholinobenzophenone, p-diacetylbenzene,4-aminobenzophenone, 4'-methoxyacetophenone, diethoxyacetophenone,benzaldehyde, and the like.

Specifically useful herein are acetophenone photosensitizers of thestructure: ##STR2## wherein R is alkyl of from 1 to about 8 carbonatoms, or aryl of 6 ring carbon atoms and R' is hydrogen, alkyl of from2 to about 8 carbon atoms, aryl of from 6 to 14 carbon atoms, or cycloalkyl of 5 to 8 ring carbon atoms.

Diethoxyacetophenone is the preferred photosensitizer.

The diisocyanate, macroglycol and chain terminator are reacted inapproximately stoichiometric amounts, i.e., in the approximate ratio of2 moles (2.0 equiv.) isophorone diisocyanate to 1 mole (1.0 equiv.)macroglycol to 2 moles (1.0 equiv.) chain terminator. At the end of thereaction between the prepolymer and the chain terminator free isocyanateis monitored by infrared spectrophotometry and, if necessary, additionalsmall amounts of the chain terminator may be added to scavenge anyremaining isocyanate. It is important that the low molecular weightmonomers present in the composition be reacted prior to contact with theskin so that only compounds with molecular weights of 1500-5000 Daltonsare present. The high molecular weight compounds do not leach out of thewound dressing into the underlying tissue and are therefore non-toxic.

An antioxidant such as tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] may be added to inhibitspontaneous oxygen-initiated curing. A polyurethane catalyst such asdioctyl tin dilaurate, N-methyl morpholine, trimethylamine,triethylamine, zinc octoate, and dibutyl tin dilaurate is added to boththe reaction medium in which the prepolymer is formed and the reactionmedium in which the prepolymer is reacted with the chain terminator.

The performed wound dressings require a material which exhibitsthixotropic behavior: a very high apparent viscosity which decreasesrapidly under shear stress. Thixotropic behavior is necessary to allowthe uncured wound dressings to conform to body geometry, and to preventsagging when the dressing is applied to vertical surfaces. Thixotropicbehavior may be induced by varying the molecular weight of themacroglycol (the higher the molecular weight, the thicker the uncureddressing); by adding a non-reactive thixotropic agent; or by acombination of the two methods. The tensile strength and hardness of thepolyurethane is also varied by varying the molecular weight of the PPG.As the molecular weight is decreased, the tensile strength and hardnessare increased. As the molecular weight is in creased, the tensilestrength and hardness are decreased.

Nonreactive thixotropic agents include pyrogenic silica such asCab-O-Sil M-5® and Cab-O-Sil N70TS® from the Cabot Company andbentonitte clays. Generally speaking, addition of 1.0 part Cab-O-SilM-5® to 100 parts urethane oligomer increases the apparent viscosity bya factor of 10,000.

To produce a thixotropic or shear-sensitive, high viscosity liquid,ultraviolet radiation curable oligomer, the vinyl terminated oligomer isdissolved together with TECOFLEX®EG-60D in an organic solvent.Preferably, 80-99 parts by wt. of the vinyl-terminated oligomer are usedper 1-20 parts by wt of said polyurethane polymer. The resultingsolution is thixotropically thickened by the addition of high surfacearea fumed silica particles. The preferred thixotropic composition isformed from 88 grams of the oligomer of Example 3 dissolved with 12grams TECOFLEX®EG-60D in 2000 grams methylene chloride, 10 grams offumed silica Cab-O-sil M-5® is added. The resulting thixotropic mixtureis suitable for the production of continuous liquid films and displays aviscosity of 370 cps at 23° C. at 20 RPM on spindle #2.

TECOFLEX® the tradename of Thermedics Inc. for a polyurethane which isthe reaction product of (1) dicyclohexyl methane diisocyanate, (2) apolytetramethylene ether polyol having a molecular weight in the range1000-3000 Daltons and (3) 1,4-butane diol and is further described inU.S. patent application Ser. No. 600,568 filed Apr. 17, 1984 in the nameof Michael Szycher, the teachings of which are incorporated herein byreference.

The presence of a thixotropic agent and the increased viscosity does notaffect cure rate since the silica particles are transparent to UVradiation.

A film of the resulting mixture can be formed by drawing, rolling, orspraying using techniques well known in the art. Optionally, the filmmay be formed on a textile fabric. Curing may be accomplished byexposure to ultraviolet radiation, typically between 219 and 425 nm for20 seconds at 0.5 W/cm². Curing transforms the liquid oligomer into asolid elastomer.

The cured polyurethane product is crystal clear, soft and elastomericand serves to release the incorporated drug at a controlled, sustainedrate while protecting that portion of the incorporated drug yet to bereleased. The product is hydrophilic in nature and solvent resistant.

Any pressure-sensitive adhesive conventionally used for wound dressingsor bandages may be spread over one surface of the cured film, e.g. apolyacrytate adhesive or a polyvinylethyl ether blend adhesive. Arelease paper or plastic film is then applied over the exposed surfaceof the adhesive.

The examples which follow serve to further illustrate the presentinvention but should not be considered as limiting; rather, the scope ofthe invention is defined by the claims which follow.

EXAMPLE 1

A four liter reactor equipped with continuous nitrogen blanketing and aheating mantel is charged with 81.6 grams isophorone diisocyanate, 245.2g of 2,000 molecular weight polypropylene glycol and 0.1% by weightdioctyl tin dilaurate.

Agitation is begun and the mixture is raised to and maintained at 60° C.After three hours, 64 grams hydroxyethyl methacrylate (HEMA) is addedwith an additional 0.1% by weight dioctyltin dilurate.

The mixture is allowed to react exothermally to 110° C. for two hours.

At the end of this reaction, free isocyanate is monitored by infraredspectrophotometry, and if necessary small amounts of hydroxyethylmethacrylate may then be added (up to 2 gm) to scavenge any remainingisocyanate.

0.1% by weight of IRGANOX 1010*, and 4% by weight diethoxy acetophenone(DEAP, a photoinitiator) is then added and the mixture agitated anddeaerated.

A film of the resulting mixture can be formed by drawing, rolling, orspraying by techniques well known in the art.

Curing may be accomplished by exposure to ultraviolet radiation,typically between 219 and 380 nanometers for 20 seconds at 0.5 watts persquare centimeter.

This results in a fully cured, solvent-resistant hydrophilic transparentelastomer with the following physical properties: tensile strength 600P.S.I., elongation 150%, hardness (shore A) 55.

EXAMPLE 2

A four liter reactor equipped with continuous nitrogen blanketing and aheating mantel is charged with 102 grams IPDI, 229.2 grams 1,000molecular weight polypropylene glycol, and 0.1% by weight dioctyltindilaurate.

Agitation is begun and the mixture is raised to and maintained at 60° C.After three hours, 59.60 grams of HEMA is added with an additional 0.1%by weight dioctyltin dilaurate.

The mixtrue is allowed to react exothermally to 110° C. for two hours.

At the end of this reaction, free isocyanate is monitored by infraredspectrophotometry, and if necessary small amounts of HEMA are added toto scavenge any remaining isocyanate.

0.1% by weight of IRGANOX 1010® and 4% by weight diethoxy acetophenoneare then added and the mixture agitated and deaerated.

A film of the resulting mixture can be formed by drawing, rolling, orspraying by techniques well known in the art.

Curing may be accomplished by exposure to ultraviolet radiation,typically between 219 and 380 nanometers for 20 seconds at 0.5 watts persquare centimeter.

This results in a fully cured, solvent-resistant, hydrophilic,transparent elastomer with the following physical properties: tensilestrength: 950 PSI, elongation 150%, hardness, (shore A) 55.

EXAMPLE 3

A four liter reactor equipped with continuous nitrogen blanketing and aheating mantel is charged with 101.6 grams IPDI, 228.8 grams 1,000molecular weight polypropylene glycol and 0.1% by weight dioctyl tindilaurate.

Agitation is begun and the mixture is raised to and maintained at 60° C.for two hours. Thereafter, 55.3 g HEMA is added with an additional 0.1%by weight dioctyltin dilaurate.

At the end of this reaction, free isocyanate is monitored by infraredspectrophotometry, and if necessary small additions of hydroxyethylmethacrylate may then be made (up to 2 gm) to scavenge any remainingisocyanate. The result is the preferred oligomer.

0.1% by weight of IRGANOX 1010® and 4% by weight diethoxyacetophenoneare then added and the mixture agitated and deaerated.

A film of the resulting mixture can be formed by drawing, rolling, orspraying by techniques well known in the art.

Curing may be accomplished by exposure to ultraviolet radiation,typically between 219 and 380 nanometers for 20 seconds at 0.5 watts persquare centimeter.

This results in a fully cured, solvent-resistant, hydrophilic,transparent elastomer with the following physical properties: tensilestrength: 950 PSI, elongation 32.5%, hardness (shore A) 60.

EXAMPLE 4

To produce a thixotropic (shear-sensitive high viscosity liquid), UVCurable Oligomer, the preferred oligomer obtained in Example 3 isco-dissolved with TECOFLEX®EG-60D (the 65 Shore D product mentioned atp. 7 in aforementioned U.S. Ser. No. 600,568) in methylene chloride. Theresulting solution is further stabilized by the addition of high surfacearea fumed silica particles as described below.

A preparation containing 94 grams of the oligomer from Example 2 isco-dissolved with 6 grams of TECOFLEX EG-60D® in 2000 grams of methylenechloride. To this solution, 10 grams of fumed silica (CAB-O-Sil N70TS®are added. The result is a thixotropic mixture, but it did not havesufficient viscosity to produce continuous liquid films.

EXAMPLE 5

A preparation containing 88 grams of the oligomer from example 3,admixed with the 0.1 wt. % IRGANOX® and 4 wt. % diethoxyacetophenone, isco-dissolved with 12 grams of TECOFLEX EG-60D® in 2000 grams ofmethylene chloride. To this solution, 10 grams of fumed silica(CAB-O-SIL M-S® are added). The result is a thixotropic mixture,suitable for the production of continuous liquid films. This mixturedisplays a viscosity of 370 cps at 23° C. 20 RPM, spindle #2, which isideal for admixture with drugs to form the wound dressings of thepresent invention, and is the preferred thixotropic UV curable mixture.

EXAMPLE 6

The constituents of example 5 are intimately mixed for 10 minutes, anddeaerated until all entrained gases are removed.

At this stage pharmacoactive substances such as 1% by weight thrombin (acoagulant) and 4% by weight gentamycin sulfate, (a wide-spectrumantibiotic) are incorporated into the above liquid by gentle mixing for30 minutes until a uniform (homogeneous) blend is obtained.

A film of the resulting mixture is then formed by drawing, rolling, orspraying as in example 1.

Curing is accomplished by exposure to U.V. radiation, typically between219 to 425 nanometers for 20 seconds at 0.5 watts/CM².

EXAMPLE 7

The constituents of example 5 are intimately mixed for 10 minutes, anddeaerated until all entrained gases are removed.

At this stage, pharmacoactive substances such as 1% by weight thrombin(a coagulant) and 6% by weight gentamycin sulfur (a wide spectrumantibiotic), are incorporated into the above liquid by gentle mixing for30 minutes until a uniform blend is obtained.

This example produced the preferred medicated UV-curable composition. Afilm of the resulting mixture may then be formed by drawing, rolling, orspraying as in example 1.

Curing is accomplished by exposure to U.V. radiation, typically between219 to 425 nanometers for 20 seconds at 0.5 watts/CM².

EXAMPLE 8

Preparation of Medicated Wound Dressings:

Supporting fabric is saturated with TECOFLEX®SG-93A (the 95 Shore Aproduct mentioned at p.7 of U.S. Ser. No. 600,568) hydrophobic polymer,by drawing the fabric vertically into a 12% solids solution of thehydrophobic polymer in chloroform. Pull speed is fully controlled sothat a continuous film enveloping the fabric is formed, having a desiredthickness of 2-4 mils.

The resulting saturated fabric is coated on one side by rolling orspraying with nitrogen the hydrophilic, thixotropic, UV-curable oligomerof Example 5, and subsequently curing the liquid into an elastomericfilm by exposing the oligomer to UV radiation between 219 and 425 nm for20 seconds at 0.5 watts/CM².

Finally, a thin coat of pressure sensitive adhesive is applied onto thecured, hydrophilic elastomeric film. The resulting multi-layeredstructure is then assembled on release paper, cut and packaged, and isready to use.

The invention may be embodied in other specific forms without departingfrom the spirit of essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:
 1. A wound dressing comprising a drug-dispensingelastomeric film, said film comprising:A. A cured reaction productconsiting essentially of:(1) isophorone diisocyanate; (2) a macroglycol;and (3) a monomer containing hydroxyl and vinyl groups; and B. apharmacoactive agent dispersed through said cured reaction product. 2.The cured wound dressing of claim 1 wherein the repeating molecularunits of said film are cross-linked through terminal vinyl groups. 3.The wound dressing of claim 1 wherein said film has been cured byincorporation of a photosensitizer and exposure to ultraviolet light. 4.The wound dressing of claim 1 wherein said reaction product is formedby:(a) reacting said isophorone diisocyanate and said macroglycoltogether in the presence of a catalyst to form an isocyanate terminatedprepolymer; (b) reacting said prepolymer with said monomer containinghydroxyl and vinyl groups to form an ultraviolet-curable, vinylterminated polyurethane oligomer; (c) admixing said oligomer with thepharmacoactive agent to form an UV-curable homogeneous blend; (d)forming the UV-curable homogeneous mixture into a film; and (e) curingsaid film by exposure to ultraviolet light.
 5. The wound dressing ofclaim 4 wherein said macroglycol is polypropylene glycol having a numberaverage molecular weight of 500-5000 daltons and said monomer ishydroxyethyl methacrylate.
 6. The wound dressing of claim 4 wherein saidfilm contains 1-10 wt. % of said drug, based on the weight of saidoligomer.
 7. The wound dressing of claim 4 wherein said drug is selectedfrom the group consisted of coagulants, antibiotics, antifungals,topical anesthetics, anti-inflammatories mixtures thereof.
 8. The wounddressing of claim 4 further comprising a coating of a pressure sensitiveadhesive on one surface of said film.
 9. The wound dressing of claim 4wherein a photoinitiator is admixed with said oligomer.
 10. The wounddressing of claim 9 wherein said photoinitiator is selected from thegroup consisting of diacetoxyacetobenzophenone, benzophenone,diethoxyacetophenone 4-morpholine benzophenone, 4-aminobenzophenone and4'-methoxyacetophenone.
 11. The wound dressing of claim 4 wherin saidfilm further comprises at least one non-reactive thixotropic agent. 12.The wound dressing of claim 11 wherein said non-reactive thixotropicagent is selected from the group consisting of pyrogenic silica andbentonite clays.
 13. The wound dressing of claim 4 wherein the vinylterminated oligomer is co-dissolved with a polyurethane polymer which isthe reaction product of:(d) dicyclohexyl methane diisocyanate; (e) apolytetramethylene ether polyol having a number average molecular weightin the range of 1000-3000 Daltons; and (f) 1,4-butane diol;and theresulting solution is formed into said film.
 14. The wound dressing ofclaim 13 wherein said film contains 80-99 parts by weight of said vinylterminated oligomer and 1-20 parts by weight of said polyurethanepolymer.
 15. The wound dressing of claim 13 further comprising a textilefabric, said film being formed on said textile fabric.
 16. The wounddressing of claim 15 wherein said textile fabric is first coated with apolyurethane polymer that is the reaction product of:dicyclohexylmethane diisocyanate; a polytetramethylene ether polyol having a numberaverage molecular weight in the range of 1000-3000 Daltons; and1,4-butane dioland then coated with said solvent solution.
 17. The wounddressing of claim 16 further comprising a coating of a pressuresensitive adhesive on one surface of said film.
 18. The wound dressingof claim 13 wherin said film further comprises at least one non-reactivethixotropic agent.
 19. The wound dressing of claim 18 wherein saidnon-reactive thixotropic agent is selected from the group consisting ofpyrogenic silica and bentonite clays.
 20. A process for forming adrug-dispensing wound dressing comprising:(1) preparing a reactionproduct consisting essentially of isophorone diisocyanate, a macroglycoland a monomer containing hydroxyl and vinyl groups by reacting (a)isophorone diisocyanate and (b) a macroglycol in the presence of acatalyst to form an isocyanate terminated prepolymer and reacting saidprepolymer with (c) a monomer containing hydroxyl and vinyl groups toform an ultraviolet-curable, vinyl terminated polyurethane liquidoligomer; (2) admixing said vinyl terminated oligomer with a drug toform an UV-curable mixture; (3) forming the UV-curable mixture into afilm; and (4) curing said film by exposure to ultraviolet light.
 21. Theprocess of claim 20 wherein a photoinitiator is admixed with saidoligomer and wherein said curing is at approximately room temperature.22. The process of claim 20 wherein said macroglycol is polypropyleneglycol having a number average molecular weight of 500-5000 daltons andsaid monomer is hydroxyethyl methacrylate.
 23. The process of claim 20wherein said drug is added in an amount 1-10% by weight, based on theweight of said oligomer.
 24. The process of claim 20 wherein said drugis selected from the group consisting of coagulants, antibiotics,antifungals, topical anesthetics, amti-inflammatories and mixturesthereof.
 25. The process of claim 20 further comprising coating onesurface of said film with a pressure sensitive adhesive.
 26. The processof claim 21 wherein said photoinitiator is selected from the groupconsisting of diacetoxyacetobenzophenone, benzophenone,diethoxyacetophenone, 4-morpholine benzophenone, 4-aminobenzophenone and4'-methoxyacetophenone.
 27. The process of claim 21 further comprisingmixing said oligomer with at least one non-reactive thixotropic agent.28. The process of claim 27 wherein said non-reactive thixotropic agentis selected from the group consisting of pyrogenic silica and bentoniteclays.
 29. A process in accordance with claim 20 wherein said vinylterminated oligomer is dissolved in an organic solvent and the drug isadmixed in said solvent solution.
 30. A process in accordance with claim29 wherein the vinyl terminated oligomer is co-dissolved with apolyurethane polymer which is the reaction product of:(d) dicyclohexylmethane diisocyanate; (e) a polytetramethylene ether polyol having anumber average molecular weight in the range of 1000-3000 daltons; and(f) 1,4-butane diol.
 31. The process of claim 30 wherein 80-99 parts byweight of said vinyl terminated oligomer are codissolved with 1-20 partsby weight of said polyurethane polymer.
 32. The process of claim 30wherein said monomer is hydroxyethyl methacrylate and said macroglycolis a polypropylene glycol having a number average molecular weight of500-3000 daltons.
 33. The process of claim 30 further comprisingproviding a textile fabric and coating said textile fabric with saidsolvent solution to form said film.
 34. The process of claim 33 wherinsaid textile fabric is first coated with a polyurethane polymer that isthe reaction product of:dicyclohexyl methane diisocyanate; apolytetramethylene ether polyol having a number average molecular weightin the range of 1000-3000 daltons; and
 1. 4-butane dioland then coatedwith said solvent solution.
 35. A process in accordance with claim 20wherein a sufficient amount of (c) is added so that only compounds withnumber average molecular weights of 1500-5000 are present. .Iadd.
 36. Adispensing elastomeric film, said film comprising:A. A cured reactionproduct consisting essentially of:(1) isophorone diisocyanate; (2) amacroglycol; and (3) a monomer containing hydroxyl and vinyl groups; andB. an agent to be dispensed through said cured reaction product..Iaddend. .Iadd.37. The cured dispensing elastomeric film of claim 36wherein the repeating molecular units of said film are cross-linkedthrough terminal vinyl groups. .Iaddend. .Iadd.38. The dispensingelastomeric film of claim 36 wherein said film has been cured byincorporation of a photosensitizer and exposure to ultraviolet light..Iaddend. .Iadd.39. The dispensing elastomeric film of claim 36 whereinsaid reaction product is formed by:(a) reacting said isophoronediisocyanate and said macroglycol together in the presence of a catalystto form an isocyanate terminated prepolymer; (b) reacting saidprepolymer with said monomer containing hydroxyl and vinyl groups toform an ultraviolet-curable, vinyl terminated polyurethane oligomer; (c)admixing said oligomer with the agent to be dispensed to form anUV-curable homogeneous blend; (d) forming the UV-curable homogeneousmixture into a film; and (e) curing said film by exposure to ultravioletlight. .Iaddend. .Iadd.40. The dispensing elastomeric film of claim 39wherein said macroglycol is polypropylene glycol having a number averagemolecular weight of 500-5000 daltons and said monomer is hydroxyethylmethacrylate. .Iaddend. .Iadd.41. The dispensing elastomeric film ofclaim 39 wherein said film containing 1-10 wt. % of said agent to bedispensed, based on the weight of said oligomer. .Iaddend. .Iadd.42. Thedispensing elastomeric film of claim 39 further comprising a coating ofa pressure sensitive adhesive on one surface of said film. .Iaddend..Iadd.43. The dispensing elastomeric film of claim 39 wherein aphotoinitiator is admixed with said oligomer. .Iaddend. .Iadd.44. Thedispensing elastomeric film of claim 43 wherein said photoinitiator isselected from the group consisting of diacetoxyacetobenzophenone,benzophenone, diethoxyacetophenone 4-morpholine benzophenone,aminobenzophenone and 4'-methoxyacetophenone. .Iaddend. .Iadd.45. Thedispensing elastomeric film of claim 39 wherein said film furthercomprises at least one non-reactive thixotropic agent. .Iaddend..Iadd.46. The dispensing elastomeric film of claim 45 wherein saidnon-reactive thixotropic agent is selected from the group consisting ofpyrogenic silica and bentonite clays. .Iaddend. .Iadd.47. The dispensingelastomeric film of claim 39 wherein the vinyl terminator oligomer isco-dissolved with a polyurethane polymer which is the reaction productof: (d) dicyclohexyl methane diisocyanate; (e) a polytetramethyleneether polyol having a number average molecular weight in the range of1000-3000 Daltons; and (f) 1,4-butane diol; and the resulting solutionis formed into said film. .Iaddend. .Iadd.48. The dispensing elastomericfilm of claim 47 wherein said film contains 80-99 parts by weight ofsaid vinyl terminated oligomer and 1-20 parts by weight of saidpolyurethane polymer. .Iaddend. .Iadd.49. The dispensing elastomericfilm of claim 47 further comprising a textile fabric, said film beingformed on said textile fabric. .Iaddend. .Iadd.50. The dispensingelastomeric film of claim 49 wherein said textile fabric is first coatedwith a polyurethane polymer that is the reaction product of:dicyclohexyl methane diisocyanate; a polytetramethylene ether polyolhaving a number average molecular weight in the range of 1000-3000Daltons; and 1,4-butane diol and then coated with said solvent solution..Iaddend. .Iadd.51. The dispensing elastomeric film of claim 50 furthercomprising a coating of a pressure sensitive adhesive on one surface ofsaid film. .Iaddend. .Iadd.52. The dispensing elastomeric film of claim47 wherein said film further comprises at least one non-reactivethixotropic agent. .Iaddend. .Iadd.53. The dispensing elastomeric filmof claim 52 wherein said non-reactive thixotropic agent is selected fromthe group consisting of pyrogenic silica and bentonite clays. .Iaddend..Iadd.54. A process for forming and dispensing elastomeric filmcomprising: (1) preparing a reaction product consisting essentially ofisophorone diisocyanate, a macroglycol and a monomer containing hydroxyland vinyl groups by reacting (a) isophorone diisocyanate and (b) amacroglycol in the presence of a catalyst to form an isocyanateterminated prepolymer and reacting said prepolymer with (c) a monomercontaining hydroxyl and vinyl groups to form an ultraviolet-curable,vinyl terminated polyurethane liquid oligomer; (2) admixing said vinylterminated oligomer with an agent to be dispensed to form an UV-curablemixture; (3) forming the UV-curable mixture into a film; and (4) curingsaid film by exposure to ultraviolet light. .Iaddend. .Iadd.55. Theprocess of claim 54 wherein a photoinitiator is admixed with saidoligomer and wherein said curing is at approximately room temperature..Iaddend. .Iadd.56. The process of claim 54 wherein said macroglycol ispolypropylene glycol having a number average molecular weight of500-5000 daltons and said monomer is hydroxyethyl methacrylate..Iaddend. .Iadd.57. The process of claim 54 wherein said agent is addedin an amount 1-10% by weight, based on the weight of said oligomer..Iaddend. .Iadd.58. The process of claim 54 further comprising coatingone surface of said film with a pressure sensitive adhesive. .Iaddend..Iadd.59. The process of claim 55 wherein said photoinitiator isselected from the group consisting of diacetoxyacetobenzophenone,benzophenone, 4-aminobenzophenone and 4'-methoxyacetophenone. .Iaddend..Iadd.60. The process of claim 55 further comprising mixing saidoligomer with at least one non-reactive thixotropic agent. .Iaddend..Iadd.61. The process of claim 60 wherein said non-reactive thixotropicagent is selected from the group consisting of pyrogenic silica andbentonite clays. .Iaddend. .Iadd.62. A process in accordance with claim54 wherein said vinyl terminated oligomer is dissolved in an organicsolvent and the agent is admixed in said solvent solution. .Iaddend..Iadd.63. A process in accordance with claim 62 wherein the vinylterminated oligomer is co-dissolved with a polyurethane polymer which isthe reaction product of:(d) dicyclohexyl methane diisocyanate; (e) apolytetramethylene ether polyol having a number average molecular weightin the range of 1000-3000 daltons; and (f) 1,4-butane diol. .Iaddend..Iadd.64. The process of claim 63 wherein 80-99 parts by weight of saidvinyl terminated oligomer are co-dissolved with 1-20 parts by weight ofsiad polyurethane polymer. .Iaddend. .Iadd.65. The process of claim 63wherein said monomer is hydroxyethyl methacrylate and said macroglycolis a polypropylene glycol having a number average molecular weight of500-3000 daltons. .Iaddend. .Iadd.66. The process of claim 63 furthercomprising providing a textile fabric and coating said textile fabricwith said solvent solution to form said film. .Iaddend. .Iadd.67. Theprocess of claim 66 wherein said textile fabric is first coated with apolyurethane polymer that is the reaction product of: dicyclohexylmethane diisocyanate; a polytetramethylene ether polyol having a numberaverage molecular weight in the range of 1000-3000 daltons; and1,4-butane diol and then coated with said solvent solution. .Iaddend..Iadd.68. A process in accordance with claim 54 wherein a sufficientamount of (c) is added so that only compounds with number averagemolecular weights of 1500-5000 are present. .Iaddend.